Although the invention will be described primarily for use to attach an auxiliary backrest to a fixed backrest in a chair, it will become evident that the adjustable attachment can be used for other purposes.
Persons who are forced to sit for long periods of time have discovered that they can improve their posture by enhancing the seat structure with the use of adjustable backrests. Such people range from clerical workers to the disabled and a variety of different types of backrests have been developed for these purposes. It will be evident that for a backrest to be suitable for a range of purposes, it should preferably be adjustable not only in terms of its shape, but also in terms of the height where it is positioned on the chair. If both adjustments are provided, then a great variety of users can be accommodated and the backrest can be adjusted as the user's needs change.